Function run 

pub fn run<A: IVm>(
    module: Module<A>,
    export: &str,
    action: Action<A>,
) -> Result<String, RunError<A>>

Evaluates a module once, selects one of its exports, reads or calls it, and renders that one value as JSON. Nothing else in the export object is called or serialized.

module is the shape generated modules expose, Module<A>, read through exports: the object of all exports, or the value the module threw, a module answering anything else refused as a thrown TypeError. A module holding a function bounds A on IStaticFunction, which naive implements.

export is looked up among the object’s own properties by presence, not by value: an export holding undefined is found, and reading it then fails as JsonError::Undefined. default is one name among them, with no fallback to it: a module without one answers NoExport("default") for it.

A call converts a clone of the selected value with Function::try_from, whose own error is a fresh TypeError, so that RunError::NotCallable holds the value the caller tried to call. It does not go through Any::call, where a value that is not a function would be a thrown TypeError, indistinguishable from the program throwing.